1. Field of the Invention
The present invention relates generally to a dust cover adapted to cover a piston rod a shock absorber in a suspension mechanism, and more particularly, to a dust cover made of resin whose upper and lower ends are adapted to attach to the shock absorber.
2. Description of the Related Art
Conventionally, there is known a dust cover which is externally fitted and mounted onto a piston rod of a shock absorber so as to cover it in an automotive suspension mechanism. The dust cover includes a bellows tube portion having peaks and valleys arranged in a linked manner, and as shown in Japanese Unexamined Patent Publication No. JP-A-2003-072338, for example, is integrally formed with a spring seat by using a rubber elastic body and attached to the piston rod at the upper end.
Meanwhile, other than the structure in which the dust cover is attached to the piston rod only at the upper end as shown in JP-A-2003-072338, it would also be possible to employ a structure as shown in U.S. Pat. No. 5,954,168. Namely, the upper end of the dust cover is attached to the piston rod and the lower end thereof is attached to the cylinder in order to prevent entry of foreign matters from below. In U.S. Pat. No. 5,954,168, a catch claw that projects from the cylinder to the outer peripheral side is inserted into a circumferential groove that opens onto the inner peripheral surface at the lower end of the dust cover and detained thereto, whereby the lower end of the dust cover is attached to the cylinder.
Besides, in the case where both the upper and lower sides are attached to the shock absorber, since a tensile load in the axial direction can be input to the dust cover, there is a risk of insufficient durability when the dust cover is made of a rubber elastic body. In light of that, a dust cover made of resin as disclosed in Japanese Unexamined Patent Publication No. JP-A-2007-032732 or the like is under study as well.
However, in order to make it possible to readily insert the catch claw into the dust cover made of resin that has less elasticity than the one made of rubber, it is necessary to set the projecting dimension of the catch claw relatively small with respect to the aperture diameter of the lower end of the dust cover. This will cause the catch claw to easily fall out from the dust cover. On the other hand, in order to prevent falling out of the catch claw from the dust cover, it is necessary to set the projecting dimension of the catch claw sufficiently large with respect to the aperture diameter of the lower end of the dust cover. This will make it difficult to insert the catch claw into the lower end of the dust cover.